1. Field of the Invention
The present invention relates to a novel slurry-phase method to produce mixed alcohols from synthesis gas by utilizing a nanosized catalyst. The catalyst is activated by nanosizing and sulfiding during catalyst preparation.
2. Discussion of the Prior Art
Synthesis gas, hereinafter "syngas" is produced from any organic/carbonaceous source, such as, but not limited to municipal solid waste (MSW), refuse derived fuel (RDF), biogas from a digester, sewage sludge, chicken manure, turkey manure, other animal and agricultural waste, corn stover, switch grass, timber, grass clippings, construction demolition materials, cotton gin waste, biomass, landfill gas, natural gas and the like. The catalytic production of mixed alcohols from synthesis gas is a well established route and the literature contains numerous examples pertaining to this transformation. Of particular interest is a method described in U.S. Pat. Nos. 4,675,344; 4,749,724; 4,752,622; 4,752,623; and 4,762,858, all originally assigned to Dow Chemical Company. These patents describe, in general, a micron-size supported catalyst based on molybdenum disulfide (MoS.sub.2). Mixed alcohols, primarily C.sub.1 -C.sub.4, i.e. methanol--butanol, are produced in good yields when the Dow catalyst is used in a packed column or fluidized bed. The best yield of oxygenates fraction is approximately 20%, on a CO.sub.2 -free basis, with up to 85% selectivity to mixed alcohols. The rate of 0.1-0.4 grams product/gram catalyst/hour is claimed by the use of the Dow catalysts at 240-325.degree. C. reaction temperature and 700-3000 psig. The above Dow patents and the references discussed and cited therein are incorporated by reference in this application.
Review of the above noted prior art and references will show that a process and catalyst that improves upon conditions of high temperature and high pressure conversion of synthesis gas to mixed alcohols, and which provides a higher conversion rate of synthesis gas to mixed alcohols per pass over/through the catalyst are highly desirable, especially for commercial applications.
For commercial application, a process that improves upon conditions of high temperature and high pressure and allows higher conversion per pass are highly desirable. To make a commercially significant alcohol process the catalyst must be highly efficient as well as the conditions in which the catalyst operates. The efficient catalyst must yield a high ratio of mass of product per given mass of catalyst in a given period of time. The catalyst must be stable and active over long periods of time before regeneration or replacement of the catalyst is required. When the feed gas has a low ratio, ideally when the H.sub.2 /CO ratio is less than 2 to 1, the catalyst will be highly selective to produce a commercial product to avoid purification or removal and disposal of by-products with the addition of a distillation tower that will split the product into two or more product streams.
When the mixture is used as a neat fuel for automobiles the presence of C.sub.1 alcohol, i.e. methyl alcohol, is more beneficial than when the alcohols are used as a commercial blend in gasoline. As used in this application, the weight ratio of methanol or C.sub.1 alcohol to C.sub.2 + alcohols means the higher alcohols, such as ethanol, propanols, butanols, etc., taken as a whole for calculation purposes. This number may be calculated by determining the weight fraction of methanol in the mixed alcohols. The esters or ethers portion of the alcohol mix are not included in either the C.sub.1 to C.sub.2 + numbers. It is therefore understood that it would be beneficial to prepare mixed alcohols, primarily C.sub.1 -C.sub.4, from synthesis gas derived from any carbonaceous source. It would also be beneficial to produce mixed alcohols in a highly efficiently manner by a catalytic method, i.e. in high yield per pass to avoid gas recycle under mild conditions of temperature and pressure.